It is conventional to desalt or dehyrate oil-continuous emulsions by introducing such emulsions directly into an electric treating field of sufficient intensity to coalesce the suspended droplets of the dispersed phase into masses of sufficient size to gravitate from the oil. The dispersed phase of such emulsions is composed of a material, usually aqueous, that is sufficiently immiscible with the oil to produce an internal or dispersed phase. Initially, the dispersed droplets are of such small size or are so stabilized that they will not readily gravitate from the oil phase. However, the electric field coalesces such dispersed droplets, and it is found that the resulting coalesced masses gravitate rapidly from the oil, usually in the same container as that in which electric treatment takes place. In a desalting operation, a quantity of water may be mixed with the incoming crude oil in a valve or other mixer, all as well known, so that a more complete removal of salt from the oil may be accomplished. Typical of such prior art dehydrator/desalters is that described in U.S. Pat. No. 2,880,158 to Delber W. Turner and a version for use on shipboard described in U.S. Pat. No. 3,736,245 to Frederick D. Watson and Howell R. Jarvis. Other related prior art U.S. Pat. Nos. are the following:
______________________________________ 2,033,446 2,527,690 2,848,412 3,250,695 3,592,756 2,072,888 2,543,996 2,892,768 3,531,393 2,443,646 2,557,847 2,894,895 3,577,336 ______________________________________
and German Pat. No. 1,014,076 (Helmut Stock; Aug. 22, 1957).
It is an object of this invention to provide a dehydrating/desalting apparatus, especially useful for desalting crude oil, that employs multiple electrode/distributor systems located in a single vessel to achieve serial stage desalting and/or vastly increased oil handling capacity in a parallel stage operation.
It is a further object of this invention to provide a process for desalting crude oil in a plurality of serial stages.
Further objects of the invention will be evident to those skilled in the art in the course of the following description.